<!DOCTYPE html>

<html>

   <head lang="en">
      <meta charset="UTF-8">
      <title></title>
      <style>
          * {
              margin: 0;
              padding: 0;
          }

          table {
              border-collapse: collapse;
              border-spacing: 0;
              border: 1px solid #c0c0c0;
              width: 500px;
              margin: 100px auto;
              text-align: center;
          }

          th {
              background-color: #09c;
              font: bold 16px "微软雅黑";
              color: #fff;
              height: 24px;
          }

          td {
              border: 1px solid #d0d0d0;
              color: #404060;
              padding: 10px;
          }

          .allCheck {
              width: 80px;
          }
      </style>
   </head>

   <body>
      <table>
         <tr>
            <th class="allCheck">
               <input type="checkbox" name="" id="checkAll"> <span class="all">全选</span>
            </th>
            <th>商品</th>
            <th>商家</th>
            <th>价格</th>
         </tr>
         <tr>
            <td>
               <input type="checkbox" name="check" class="ck">
            </td>
            <td>小米手机</td>
            <td>小米</td>
            <td>￥1999</td>
         </tr>
         <tr>
            <td>
               <input type="checkbox" name="check" class="ck">
            </td>
            <td>小米净水器</td>
            <td>小米</td>
            <td>￥4999</td>
         </tr>
         <tr>
            <td>
               <input type="checkbox" name="check" class="ck">
            </td>
            <td>小米电视</td>
            <td>小米</td>
            <td>￥5999</td>
         </tr>
      </table>
      <script>
         const checkAll = document.querySelector('#checkAll')
         // console.log(checkAll.checked)
         const cks = document.querySelectorAll('.ck')
         checkAll.addEventListener('click', function () {
            console.log(checkAll.checked)
            for (let i = 0; i < cks.length; i++) {
               console.log(cks[i])
               cks[i].checked = this.checked
            }
         })
         for (let i = 0; i < cks.length; i++) {
            cks[i].addEventListener('click', function () {
               // console.log(document.querySelectorAll('.ck:checked').length)
               checkAll.checked = document.querySelectorAll('.ck:checked').length === cks.length
            })
         }
      </script>
   </body>

</html>